Ecological and Parasitological Study on Cerithidea cingulata (Gastropoda) in Hormoz Strait Littoral, South of Iran.

Background
"Cerithidea cingulata" is reported from south of Iran, may act as intermediate host of Heterophyes heterophyes and cercaria dermatitis. As parasitological aspects of this brackish snail were not studied in Iran, this study was conducted in 2016, in Hormoz Strait, south of Iran.


Methods
Totally 402 snails were collected from 36 locations of three main regions in Hormozgan Province, Iran in 2015. In each location, one square meter was checked, and snails were collected for parasitological study. Snails were crashed and cercariae were studied using light microscope, in some cases natural red staining was used for better resolution.


Results
Mean length of snails was about 20.33 mm, width 5.57 mm. The aperture length was 5.10 and spire was 15.22. Important founded cercaria was cysticercus cercariae, echinostoma cercaria, furcocercus cercaria, furcocystocercous cercaria, gastrostomy cercaria, gymnocephalus cercaria, monostome cercaria, pelurolophocercus cercaria and xiphidiocercaria.


Conclusion
The presence of this snail is reported from Persian Gulf to western Pacific in China. Our study showed a pattern of infection in local area and was compatible with other studies. Importance of C. cingulata as intermediate host of some medically important disease should be considered and other complementary molecular studies for exact identification of cercaria are necessary.

Hormoz Strait is an important area in south of Iran, where the Persian Gulf (2) is separated from Oman Sea. Ecology of this area is affected by three zoogeographic zones, Sahero-Arabian in south Palearctic in north and Indo-Malayan in east (3). Epidemiological condition of disease in north of Persian Gulf and Oman sea is almost different from other parts of Iran. While most parts of Iran is known as Palearctic zoogeographical area, south of Iran may consider in Afrotropicallike and Indomalayan-like subzones. Some diseases like Schistosomiasis, Dracunculiasis (4) and Heterophyasis (5) were reported from this area and not from northern parts. Combination of different climatologic and zoogeo-graphic realm and zones in Iran produce a complex epidemiological condition.
Brackish water or sea snails have less medically importance but "Pirenella conica" is known as intermediate host of "Heterophyes heterophyes" in some parts of the world (6). "C. cingulata" was reported from south of Iran (7) in 2011 for the first time (8), however, its parasitological importance as an intermediate host is not well studied in Iran.
For better understanding the role of "C. cingulata" in ecology and epidemiology of probable disease in specific local condition, this study was conducted in 2016 in Hormoz Strait, south of Iran.

Study area
Totally, 402 snails were collected from 36 locations of three main regions in Hormozgan Province, adjust to Hormoz Strait, including "Khamir", "Bandar-Abbas" and "Qeshm" districts in 2016 ( Fig. 1).  In the study area, 36 locations were considered as suitable niche for snail colonies while  33 were success and 3 locations were empty. In each location, a 1x1 meter area was isolated by four 1 m wooden scale. Ecological condition of water was checked using portable multimeter (pH, EC, TDS, Salt, and thermometer) Model TS7200 MIC company. A portable oxygen meter (AZ Model 8403) was used for measuring dissolved oxygen. Ecological variable measurements were, Water temperature (Celsius Degrees; C), pH, Total Dissolved Salts (TDS in ppm), Oxygen (ppm), considering equal amount of Oxygen and Dissolved Salt, these variables were excluded.
Snails were transmitted to Hormozgan University of Medical Sciences, General Laboratory and were checked using crash method (9). Some suitable samples were stained using lactophenol methylene blue and natural-red and diagnosed by light microscopy. Cercaria density in each snail was recognized as Light, Moderate, Heavy and Very heavy. From some suitable samples, film and photography were taken and taken. We used a Neubauer chamber scale for calibrating microscope and measuring the size of cercaria in this study. Measurement was done using Image J 1.5i, National Institutes of Health-USA.
Results were arranged in SPSS 20, (

Ecology and Conchology of C. cingulata
Neglecting full grown snails or not, mean length of snails was 20.33 ± 7.85 mm, with mean width of 5.57 ± 0.67 mm. The aperture length was 5.10 ± 0.65 mm spire was 15.22 ± 5.02; Spire/Aperture rate was ~3/1. Full grown snails had 6 to 7 brownish tuberculated whorls with semi deteriorated apex. Fig. 2 shows a sample of these snails. Snails were collected from suitable niche in Hormoz Strait shore. Concerning low slope of shore, these samples were not adjusted to the water, interestingly bigger colonies had more distance from water in comparison with colonies in depth of shore; while 2.5% of samples were exactly in the water, 55.3% had considerable distance from water.
The average of water pH in the adjusted colonies was 8.06 ± 0.4, from minimum 7 to maximum 8.9. ANOVA analysis between grouped density and pH show statistical correlation (P=0.001) (Fig. 3-Part D).
The water pool had temperature from 22 to 39.5 with average of 34.00 ± 4.16. Mean of snails in one square meter was 155.42 with median 102, from minimum 10 to maximum 725.
1-echinostoma cercaria This cercaria was found in 11 snails. It may be considerd in two categories, based on size of the tail. About 2.73% of snails were infect-ed to this kind of cercaria in which 1% had moderate and 1.7% had heavy infection. Two subtype echinostome cercaria may be considerd as follows: The first was short tail cercaria with 600-610 µm body and 180 -190 µm tail. (Fig 4-1-B) The second echinostoma cercaria with long tail; in this case body has 410-420 µm with 330-310 µm. (Fig 4-1-A). Fig. 4-1 shows two samples of this cercaria type.

Furcocercus cercaria
This cercaria was found in 40 snails and with 9.95%. Four different types of furcocercaria were seen in this study, including classic featured furcocercaria in two different sizes, with blunt shaped tale and with eyespot. 9.95% of snails have infected to this cercaria it was the most pollutant cercaria in the study areas. Eight percent of snails were highly infected to this cercaria. Figure 4-2 shows three sub-types of furcocercaria (Fig.4-2-A to 4-2-C). Furcocercaria in bigger size had a body with 360-370 micrometer the tail was 360-370 µm with two typical branches with 300-310 µm ( Fig. 4-2-A).
Furcocystocercous cercaria was found in 9% of snails. Cercariae had body with 90-100 µm. the tail was about 65 µm and unlike others very oval shaped blunted tail end with two small blunted branches about 35 µm (Fig. 4-3).
Snails with infection with this cercaria were distributed around Bandar-Abbas and Bandar-Pol. Figure 3-B shows map of infected snail distribution.

Cystocercous cercariae
Only one snail was moderately infected to this kind of cercaria. This cercaria had 240 µm length for body and 1900 to 2000 µm for tail. Eyespot was presented (Fig. 4-4).

Gymnocephalus cercariae
There were 6 snails moderately infected to this cercaria. Hydrocephalus with long shaped morphology had a body about 690-700 with a tail with about 510-520µm (Fig. 4-6).

Monostomun
Two sub-types of cercaria with one sucker were found in C. cingulata around Hormoz Strait, one smaller with eye spots and the second larger without eyespot.
Monostom cercaria with eyespot; from 12 infected snails 11 had moderate infection and one snail had very heavy infection to this cercaria. Size of body was about 155 with tail of 106 micrometer.

Nematode Larvae
This study shows infection of 12 snails to Nematode larvae. Mean size of these larvae was 350-370 µm in length. Fig. 4-8 shows distributional map of infected snails which are focused around Bandar-Abbas.

Pelurolophocercus cercaria
Fifteen snails were infected with pelurolophocercus cercaria. Concerning morphological criteria, two morphological variations, were seen. The first cercaria had a round body 125 µm length x 113 µm width; its tail has 245 µm lengths (Fig. 4-9-A). Second pleurocercus cercaria had 160 µm length body and 426 µm tail (Fig. 4-9-B). In both cases, fin fold is not well projected in photography. Distribution of snails, infected with pleurolophocercus is similar to furcocercaria.

Redi and Sporocyst
This study showed 77 snails were infected to different redi and/or sporocyst of trematoda. Typical size of these forms was 630 -650 µm x 115-120 µm.

Cercarium and Undiagnosed Cases
In addition to many crashed cercaria, segmented parts like tails or bodies which may not be identified, one case of micro cercaria and a case of unknown cercarium-like cercaria were seen, which had a rostellum like organ ( Fig. 4-12).

Discussion
The first available document about presence of C. cingulata in Iran refers to 2011 (10) and this is the first and only study on ecology and parasitological aspects of C. cingulata in Iran. Presence of this snail is reported from Persian Gulf (11) to western Pacific in China (12). Another species of Cerithidea found in East Africa, where mangrove tree trunk may be found (13). Although Mangrove Forest is very close to our study area, there was not exactly in our sampling zone. Our findings on prevalence of different types of cercaria are compatible with studies of Nomchote in Thailand (10).
Our study shows infection of snails was not distributed normally; i.e. there were two high infected zones around Bandar Abbas and in the second rank Bandar-Khamir. While there was not any infected snail in the southern shore of Qeshm island, adjust to main areas of Hormoz Strait, where seagulls are more prevalent, most infected area with highest infection rate of snails was around the Bandar Abbas, capital of the province, with highest population density in the area. Source of snail infections was creek drainage coming from the land and seagull have less importance. The most prevalent cercaria in this study was furcocercaria.
Molecular studies in near area shows that it may act as Cercaria dermatitis agent (14) and is parallel to our findings on furcocercus cercaria.

Conclusion
Freshwater snails are main intermediate hosts of trematoda and brackish water snails are have not any importance in public health but this study which is first study on brackish water snail shows probable importance of this snails in public health as probable intermediate host of H. heterophyes, concerning the reported pelurolophocercus cercariae. Complementary molecular studies on these cercariae and exact identification may be conducted by further research.